大型锅炉房的噪声监测与治理

对大型锅炉房(燃煤、燃气、燃油)的噪声源进行测试分析．给出了隔声、吸声、消声量的计算公式．同时针对燃煤、燃油、燃气锅炉房的噪声污染．采取了不同的治理措施．取得了较好的治理效果。     

甘肃省作物布局演变及其对区域气候变暖的响应

根据甘肃省1985-2005年的气候资料和同时期主要作物播种面积等统计资料,利用快速聚类分析方法分析了气候变暖背景下甘肃省主要作物的种植格局和种植界限演变情况。结果表明:过去20 a里特别是进入20世纪90年代,在河西地区,玉米和棉花播种范围扩张趋势明显,种植面积比重显著增加,春小麦种植面积比重快速降低,种植范围大幅向祁连山浅山区退缩,种植结构的这种调整使玉米和棉花逐渐取代小麦成为河西主要作物,并最终导致该区主要作物种植格局从以小麦为主转变为以玉米和棉花为主;在中部地区,春小麦面积逐年缩小,冬小麦和杂粮种植扩张,玉米的种植比例逐年上升,马铃薯种植逐渐形成规模,形成了以小麦和玉米为主的种植格局;在东南部地区,春小麦和冬小麦面积逐年缩小,玉米、冬油菜和其他喜温的经济作物种植比例逐年上升。相关分析表明,上述作物种植格局的变化与气候变暖带来的积温增加及积温带北移东扩密切相关。     

Measurement of air exchange rates in different indoor environments using continuous CO2 sensors

A new air exchange rate (AER) monitoring method using continuous CO₂ sensors was developed and validated through both laboratory experiments and field studies. Controlled laboratory simulation tests were conducted in a 1-m³ environmental chamber at different AERs (0.1-10.0 hr^-1). AERs were determined using the decay method based on box model assumptions. Field tests were conducted in classrooms, dormitories, meeting rooms and apartments during 2-5 weekdays using CO₂ sensors coupled with data loggers. Indoor temperature, relative humidity (RH), and CO₂ concentrations were continuously monitored while outdoor parameters combined with on-site climate conditions were recorded. Statistical results indicated that good laboratory performance was achieved: duplicate precision was within 10%, and the measured AERs were 90%-120% of the real AERs. Average AERs were 1.22, 1.37, 1.10, 1.91 and 0.73 hr^-1 in dormitories, air-conditioned classrooms, classrooms with an air circulation cooling system, reading rooms, and meeting rooms, respectively. In an elderly particulate matter exposure study, all the homes had AER values ranging from 0.29 to 3.46 hr??1 in fall, and 0.12 to 1.39 hr^-1 in winter with a median AER of 1.15.     

Ammonium-dependent regulation of aerobic methane-consuming bacteria in landfill cover soil by leachate irrigation

The impacts of landfill leachate irrigation on methane oxidation activities and methane-consuming bacteria populations were studied by incubation of landfill cover soils with leachate and (NH₄)₂SO₄ solution at different ammonium concentrations. The community structures and abundances of methane-oxidizing bacteria (MOB) and ammonia-oxidizing bacteria (AOB) were examined by PCRDGGE and real-time PCR. Compared with the pure (NH₄)₂SO₄ solution, leachate addition was found to have a positive effect on methane oxidation activity. In terms of the irrigation amount, ammonium in leachate was responsible for the actual inhibition of leachate. The extent of inhibitory effect mainly depended on its ammonium concentration. The suppression of the predominant methaneconsuming bacteria, type I MOB, was responsible for the decreased methane oxidation activity by ammonium inhibition. Methaneconsuming bacteria responded diversely in abundance to ammonium. The abundance of type I MOB decreased by fivefold; type II MOB showed stimulation response of fivefold magnification upon the first addition but lessened to be lower than the original level after the second addition; the amount of AOB was stimulated to increase for 20-30 times gradually. Accumulated nitrate from nitrification strengthened the ammonium inhibition on type I and type II MOB, as a result, repetitive irrigation was unfavorable for methane oxidation.     

Effects of rare earth elements La and Yb on the morphological and functional development of zebrafish embryos

In recent years, with the wide applications and mineral exploitation of rare earth elements, their potential environmental and health effects have caused increasing public concern. Effect of rare earth elements La and Yb on the morphological and functional development of zebrafish embryos were studied. The embryos were exposed to La³⁺ or Yb³⁺ at 0, 0.01, 0.1, 0.3, 0.5 and 1.0 mmol/L, respectively. Early life stage parameters such as egg and embryo mortality, gastrula development, tail detachment, eyes, somite formation, circulatory system, pigmentation, malformations, hatching rate, length of larvae and mortality were investigated. The results showed La³⁺ and Yb³⁺ delayed zebrafish embryo and larval development, decreased survival and hatching rates, and caused tail malformation in a concentration-dependent way. Moreover, heavy rare-earth ytterbium led to more severe acute toxicity of zebrafish embryo than light rare-earth lanthanum.     

Operating condition influences on PCDD/Fs emissions from sinter pot tests with hot flue gas recycling

This study was designed to clarify the influence of operating conditions on the formation and emissions of polychlorinated-pdibenzodioxins and dibenzofurans (PCDD/Fs) from a sintering process with hot flue gas recycling. A pilot scale sinter pot with simulated flue gas recycling was developed, and four key operational parameters, including temperature, oxygen content of the simulated waste flue gas, the coke rate of the sintering mixture, and the quicklime quality, were selected for exploring PCDD/Fs formation. The results showed that the temperature of the recycled flue gas had a major affect on PCDD/Fs formation, and a high temperature could significantly increase their formation during sintering. A clear linear correlation between the temperature of recycling flue gas and PCDD/Fs emission (r = 0.93) was found. PCDD/Fs could be reduced to a certain extent by decreasing the level of oxygen in the recycled flue gas, while sintering quality was unchanged. The coke rate had no significant influence on the formation of PCDD/Fs, but the quality of quicklime used in the sintering mixture could affect not only the amount of PCDD/Fs emissions but also the sintering productivity. Compared with a benchmark sinter pot test, PCDD/Fs emissions markedly decreased with improvements to quicklime quality. However, the reduction in PCDD/Fs emissions realized by using high-quality quicklime was limited by the temperature of the inlet gas. The highest reduction achieved was 51% compared with conventional quicklime when the temperature of the inlet gas was 150°C.     

Three-dimensional hydrodynamic and water quality model for TMDL development of Lake Fuxian, China

Lake Fuxian is the largest deep freshwater lake in China. Although its average water quality meets Class I of the China National Water Quality Standard (CNWQS), i.e., GB3838-2002, monitoring data indicate that the water quality approaches the Class II threshold in some areas. Thus it is urgent to reduce the watershed load through the total maximum daily load (TMDL) program. A three-dimensional hydrodynamic and water quality model was developed for Lake Fuxian, simulating flow circulation and pollutant fate and transport. The model development process consists of several steps, including grid generation, initial and boundary condition configurations, and model calibration processes. The model accurately reproduced the observed water surface elevation, spatiotemporal variations in temperature, and total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) concentrations, suggesting a reasonable numerical representation of the prototype system for further TMDL analyses. The TMDL was calculated using two interpretations of the water quality standards for Class I of the CNWQS based on the maximum instantaneous surface and annual average surface water concentrations. Analysis of the first scenario indicated that the TN, TP and COD loads should be reduced by 66%, 68% and 57%, respectively. Water quality was the highest priority; however, local economic development and cost feasibility for load reduction can pose significant issues. In the second interpretation, the model results showed that, under the existing conditions, the average water quality meets the Class I standard and therefore load reduction is unnecessary. Future studies are needed to conduct risk and cost assessments for realistic decision-making.     

Aerosol structure and vertical distribution in a multi-source dust region

The vertical distribution of aerosols was directly observed under various atmospheric conditions in the free troposphere using surface micro-pulse lidar (MPL4) at the Zhangye Station (39.08°N, 100.27°E) in western China in the spring of 2008. The study shows that the aerosol distribution over Zhangye can be vertically classified into upper, middle and lower layers with altitudes of 4.5 to 9 km, 2.5 to 4.5 km, and less than 2.5 km, respectively. The aerosol in the upper layer originated from the external sources at higher altitude regions, from far desert regions upwind of Zhangye or transported from higher atmospheric layers by free convection, and the altitude of this aerosol layer decreased with time; the aerosols in the middle and lower layers originated from both external and local sources. The aerosol extinction coefficients in the upper and lower layers decreased with altitude, whereas the coefficient in the middle layer changed only slightly, which suggests that aerosol mixing occurs in the middle layer. The distribution of aerosols with altitude has three features: a single peak that forms under stable atmospheric conditions, an exponential decrease with altitude that occurs under unstable atmospheric conditions, and slight change in the mixed layer. Due to the impact of the top of the atmospheric boundary layer, the diurnal variation in the aerosol extinction coefficient has a single peak, which is higher in the afternoon and lower in the morning.     

基于支持向量机的湖泊生态系统健康评价研究

利用支持向量机在处理分类问题、小样本问题和泛化推广方面的优势,构建了基于支持向量机的湖泊生态系统健康评价模型.同时,对广州市最大的人工湖——白云湖的水质及生物群落情况进行了监测,最后运用该模型对白云湖生态系统健康状况进行了评价.评价结果表明,白云湖生态系统处于病态状态,不能达到其净化水质的设计作用.建议从提高进水水质、实施湖区截污和丰富生物量3方面改善白云湖生态系统健康水平.与传统熵权综合健康指数法和熵权模糊综合评价法相比,所建模型更加客观、科学地评价了湖泊生态系统健康状况,能够为湖泊生态系统健康管理提供一定依据,具有广阔的应用前景.     

脉冲电絮凝处理三次采油污水研究

文章利用自制的脉冲电絮凝装置对油田三次采油污水进行了处理,讨论了脉冲电流参数,包括脉冲峰值电流、频率、占空比的影响,并通过正交实验优化了处理条件。在优化条件下处理后,油田三次采油污水的COD和浊度分别达到66.3 mg/L和1.5 FTU,满足国家《污水综合排放标准》的要求。同时,脉冲电絮凝法处理三次采油污水的效果优于投加聚合氯化铝和聚合硫酸铁的化学处理法,在处理效果和节省电能的方面明显优于直流电絮凝方法。